In order to acoustically insulate the passenger cabin or the cargo compartment of an aircraft from external noises such as, for example, engine noises, the inside of an aircraft fuselage is frequently lined with insulating mats of glass wool. In this case, the insulating mats line the fuselage frames as well as the frame panels situated between the individual frames including the stringers. The insulation is fastened on the frame panels as well as on the frames that laterally border the frame panels with the aid of fir tree-shaped fastening needles and fastening disks pressed thereon as illustrated in an exemplary fashion in FIG. 1.
According to this figure, the insulation is substantially compressed in the region of the fastening needles in this fastening method such that the cover foils of the insulating mats are compressed or contracted. In these regions, however, where the insulation is compressed, the acoustic effect of the insulation is inferior to the same quantity of insulating material in its original thickness. In addition, the cover foil of the insulating mats is stretched over the disks fastened on the fastening needles such that the cover foil is disadvantageously subjected to vibrations originating from the aircraft fuselage via the fastening needles and the disks. The thusly induced vibrations are emitted in the form of noise waves via the funnel that results from the compression of the cover foil and is clearly visible in FIG. 1 similar to a loudspeaker such that the noise contamination may increase.
FIG. 1 furthermore shows that the insulating mat is substantially compressed in the region of the frames such that undesirable acoustic and thermal bridges are also created at these locations.